Field of the Invention
The present invention relates to sheet feeding apparatuses configured to feed sheets to apparatuses such as image forming apparatuses and to image forming apparatuses.
Description of the Related Art
Sheet feeding apparatuses adopted in image forming apparatuses such as printers, copying machines or facsimiles are usually equipped with a pickup member to pick up sheets supported on a sheet supporting portion, and a conveyance member to receive and convey the sheets fed by the pickup member. Further, some sheet feeding apparatuses adopt a configuration in which a pickup member is relatively moved with respect to the sheets along with the driving of the pickup member, so that the pickup member picks up the sheets one by one by performing a pickup operation in which the pickup member comes in contact with the sheet supported on the sheet supporting portion, and then the contact state is released.
Japanese Unexamined Patent Application Publication No. 2012-017169 discloses a sheet feeding apparatus in which a sheet supporting portion is lifted and lowered by a cam that rotates along with the rotation of a sheet feed roller. A sheet supported on the sheet supporting portion comes in contact with a sheet feed roller, and thereafter, the contact of the sheet with the sheet feed roller is released. This document also discloses a configuration in which after the sheet is fed from the sheet feed roller by the lifting of the sheet supporting portion, the sheet supporting portion is raised again so that the sheet contacts the sheet feed roller, thereby the sheet feed roller assisting the conveyance of the sheet by a registration roller pair.
However, in the course of improving stability of conveyance of sheets by carrying out pickup operations multiple times by the pickup member, there were cases where a sheet stacked below the uppermost sheet being fed, hereinafter referred to as a succeeding sheet, is picked up undesirably by the pickup member. For example, in a case where the pickup operation is executed twice by the pickup member, there were cases where a trailing edge of the uppermost sheet passes an abutment position, where the pickup member abut with sheets, before the second pickup operation is completed. Then the pickup member comes in contact with the succeeding sheet, such that the succeeding sheet starts moving. The succeeding sheet is fed from the sheet supporting portion along with the feeding of the uppermost sheet, thereby causing undesirable situations such as occurrence of multiple feeding of sheets.